It is known at connecting devices with connecting members having holes and tubular connecting members fitting thereto, to design the holes and the tubular members with four, five or six corners. The purpose of designing the holes and the tubular members respectively, in this way is that connection of a tubular member to a hole shall be possible only if the shapes thereof correspond exactly with each other.
However, it has been found that one by means of polygonal tubular members and holes can not entirely exclude misconnections since one by using force during connection can deform the members in which the holes are provided and/or the tubular members such that one thereby obtains an acceptable fit between said members.
Thus, it is possible to closely connect cylindrical connecting members, i.e. tubular members of ordinary shape, to connecting members having holes, wherein the holes are polygonal, so that one moves the cylindrical connecting member into the hole with such a force that the edges thereof are deformed and bent inwards until the hole gets a circular shape into which the tubular member fits.